Micro CH 6

Question 1

State the Central Dogma of molecular biology ?

Answer 1

Theory stating that genetic information flows only in one direction, from DNA, to RNA, to protein, or RNA directly to protein.

Question 2

Know the structure of nucleotides, and be able to describe the structure of DNA

Answer 2

Nucleotides consists of deoxyribose, base (A,C,G,or T) and a phosphate group.

Question 3

Properties of Double Helix

Answer 3

• Nucleic acid backbone (alternating bases)
• Phosphodiester bonds connect 3 carbon sugar to 5 carbon sugar
• Negatively charged molecules
• Antiparallel
• Complementary base-pairing
• Double strands held together by hydrogen bonds between bases
• contains two grooves, major and minor

Question 4

Size and Supercoiling

Answer 4

• Linear DNA length several times longer
• Supercoiled: a double helix (as of DNA) that has undergone additional twisting in the same direction as or in the opposite direction from the turns in the original helix
• DNA breaks and then twists up break is then resealed by DNA gyrase
• Supercoil Insertion (DNA gyrase): in produces supercoils into DNA via double-strand breaks (negative: twisted in opposite)
  (positive: helps prevent DNA from melting at high temp)
• Supercoil removal (topoisomerase) relaxes overwound DNA that forms upstream during replication and transcription

Question 5

Replication

Answer 5

DNA is duplicated by DNA polymerase; this occurs before the onset of binary fission

Question 6

Transcription

Answer 6

information from DNA is transferred to RNA (mRNA) by RNA polymerase

Question 7

Translation

Answer 7

Information in mRNA is used to build polypeptides on ribosome

Question 8

RNA types

Answer 8

• mRNA (messenger RNA): template (message) for protein synthesis
• tRNA (transfer RNA): carries amino acids to the site of protein synthesis
• rRNA (ribosomal RNA): catalytic and structural components of the ribosomal complex- the actual sit of protein synthesis

Question 9

Difference between DNA in Eukaryotes vs Prokaryotes?

Answer 9

Eukaryotes
- Replication and transcription occur in nucleus
- RNAs must be exported outside nucleus for translation
Prokaryotes
- Multiple genes may be transcribed in one mRNA
- Coupled transcription and translation occur, providing proteins at maximal rate

Question 10

Transposable elements

Answer 10

• Repetitive DNA sequences that are inserted into other DNA molecules
• They can move from one sit to another site on the same or different DNA molecule (chromosomes, plasmids, viral genomes)
• Can result in mutation, alter gene expression, induce chromosomal rearrangements

Question 11

Plasmids (extrachromosomal DNA)

Answer 11

• Circular (common) or linear (rare) double stranded DNA that replicates separately from chromosomes
• found in Bacteria and Archaea
• toxin production or antibiotic resistance
• present in different copy number

Question 12

R plasmid

Answer 12

• Resistance plasmids: confers resistance to antibiotics or other growth inhibitors
• Several antibiotic resistance genes can be encoded on one R plasmid